EXPO-12: Development and validation of the Exposure to Violent Extremism Scale.

Objective: This study details the development and validation of the 12-item Exposure to Violent Extremism Scale (EXPO-12). We aimed to undertake a transparent and robust process of scale development to present a tool to facilitate research on the relationship between exposure and violent extremism. / Method: First, we generated an initial item pool and evaluated items via expert feedback (n = 6) and a task designed to assess item comprehension (n = 13; Study 1). Second, we explored the underlying factor structure with exploratory factor analysis (EFA) and evaluated item characteristics with item response theory (IRT) in a representative sample of the U.K. population (n = 1, 509; Study 2). Finally, we sought to replicate the factor structure proposed by Study 2 via confirmatory factor analysis (CFA) and examined convergent validity with a related construct, violent extremist intentions (n = 1, 475; Study 3). / Results: Study 1 resulted in a preliminary pool of 40 items. Study 2 used EFA to establish a four-factor structure consisting of 21 items. IRT further reduced the item pool by evaluating differential item functioning, discrimination, and location parameters, resulting in EXPO-12. Study 3 replicated the factor structure proposed in Study 2 via CFA. EXPO-12 demonstrated good convergent validity with violent extremist intentions. / Conclusion: EXPO-12 is presented as a preliminarily validated measure of the concept, alongside its limitations. The scale’s main implication is as a tool to facilitate research to unpack the complexity and nuances of the relationship between exposure and violent extremism.